GDA backend status - Dec 9, 2006
Based on r15090
Merged with r15803

Building:
- I am currently building with libgda 1.99.1 installed in /opt/libgda-1.99.1.
Configure.in will use pkg-config to set up the include and lib information.
This cannot be overridden (yet) by any switch on the ./configure command.

Execution:
- A basic GDA backend framework now exists.  This framework accepts URLs of
the form gda://DSN:USERNAME:PASSWORD.  "gda" is required.  "DSN" represents
a dataset configured in ~/.libgda/config.  USERNAME and PASSWORD are not
required but can be specified.

- The backend assumes that the database already exists.  Tables will be
created if they don't exist.  I have only tested with mysql.  In theory, other
db engines supported by libgda should work correctly.

- The backend will save commodities and load them on startup.
- The backend will save accounts and load them on startup.  Accounts created
for scheduled transactions will be loaded into the CoA.
- The backend will save budgets and load them on startup.
- The backend will save lots and load them on startup.
- The backend will save prices and load them on startup.

- Don't use scheduled transactions.  An account and a scheduled transaction
will be saved.  Frequency info will not be saved/restored.  Other related info
will not be saved/restored.

- Slots will be saved and restored for all objects.

- When a register is opened, splits and transactions will be queried.  If a
transaction is created or edited (I haven't tested deletion yet), the db is
updated properly.

Libgda Issues:
- There is a bug in libgda.  Dates are not saved.  libgda creates the SQL as
'MM-DD-YYYY' instead of 'YYYY-MM-DD'.  MySQL doesn't complain, but stores the
date as '0000-00-00'.  Fixed in libgda CVS.

GC and GDA Backend Issues:
- To avoid having the backend commit everything twice (because of the Qof two
phase commit protocol), saved objects are marked clean when committed.  To do
this, I need to reach right into the QofInstance structure and clear the dirty
flag.  There should be a better way to do this.  Note this also keeps the book
from being marked dirty.  Q: If a db backend becomes the standard and xml
is only for import/export, does the concept of clean/dirty disappear?

- Recurrences are currently only used by budgets, and recurrence save/restore
is included in the budget save/restore code.  If recurrences will eventually
be used elsewhere in GC, recurrence save/restore code may need to be split out
on its own (separate recurrences table?)

- The backend has its own tables for objects which include db-related info.
Can these be merged with the engine object tables?

- When a price is committed, the priceDB is also committed.  Could there
eventually be multiple priceDBs?  If not, the priceDB commit is just ignored.

- Multiple books?  The old postgres backend had a books table.  If the new
db should have one, accounts (and other objects) should have a book guid field.

- If I try to "Save As" and type a url (e.g. gda://xxx), this gets converted
to file:///home/phil/.../gda%3F%2A%2Axxx.  (I don't remember the % escapes 
exactly, but you get the picture).  I tried adding
gtk_file_chooser_set_local_only( file_box, FALSE) but that didn't help.

TODO:
- Add --with-libgda= configure option

- Business objects

- Check for memory leaks

- Better representation for gnc_numeric - doesn't compare well i.e. a query
for splits where 'value > 20.00' will be difficult.  Maybe should convert
gnc_numeric <-> double.

- Queries - Split query is handled specially because it is quite involved.
Only other query I've seen is by the business backend for invoices due soon.
Generic query handler not built yet.

- SQLite if just a "file".  If the file being opened is an SQLite db, should
be handled properly.  If a file is saved as file://xxx, xxx should be created
as a SQLite db.  Perhaps xml://  should be used for xml interchange format.

- Finish scheduled transactions